Multilayer ceramic capacitors and inductors consist of a plurality of interleaved and staggered layers of an electrically conductive film of metal (termed "electrode"), formed by the deposition (usually by screen printing or variations thereof) of a thick film paste (termed an "electrode composition") and electrically insulating layers of a ceramic oxide (termed "dielectric"), formed by laying a cast dielectric tape or by casting a dielectric slurry over the dried electrode. Such capacitors and inductors are well-known in the art. U.S. Pat. No. 2,389,420, for example, describes the structure, manufacture and properties of monolithic multilayer ceramic capacitors formed using cast dielectric green (unfired) tape.
The electrode composition is usually a dispersion of finely divided precious metal powders, such as palladium, silver, gold, or platinum or their mixtures, in a vehicle or carrier which is usually solely organic in nature. Dispersions of non-precious metals such as copper and nickel have also been shown to have utility in electrode compositions. The vehicle is usually composed of a mixture of a polymeric resin which imparts viscosity to the composition and appropriate solvents for processing compatibility, particularly with respect to drying. Other organic additives are usually made to the vehicle to control paste rheology. Typical electrode composition metal concentrations range from 40% to 70% by weight, with the remainder being vehicle. Electrode compositions are deposited, usually by screen printing techniques, on dried dielectric layers, then dried to remove solvents and leave a mixture of metal powders and resin from the vehicle.
The dielectric layer is usually composed of finely divided oxide powders dispersed in a resin to form a slip. This slip is then cast to form green dielectric tape. Barium titanate (BaTiO.sub.3) and other oxides such as neodymium titanate (Nd.sub.2 Ti.sub.2 O.sub.7) and magnesium titanate (MgTiO.sub.3) are used. Additions are usually made to these oxides to control various electrical characteristics, particularly to maximize dielectric constant while controlling the temperature dependence of dielectric constant and insulation resistance, among other properties. The resin is present in the dielectric layers to facilitate casting, handling and printing of electrodes on the layers.
Multilayer ceramic capacitors are manufactured by building up an interleaved configuration of electrode and dielectric layers, dicing individual parts out of the build-up then subjecting the parts to a slow burnout and then high temperature firing. Burnout is done to remove the organic resin in the electrode and dielectric layers to avoid rapid outgassing and rupture of the parts. Firing is done to a peak temperature (the "dielectric maturation temperature") both to densify the dielectric for maximum dielectric constant and physical strength, and to react the chemical constituents of the dielectric so that other desired electrical characteristics are achieved. During the firing step, the powder grains in the electrode layers also sinter and densify so as to produce a continuous, highly electrically conductive metal film.
U.S. Pat. No. 4,954,926, issued to Pepin, relates to thick film conductor compositions. The thick film conductor composition comprises (A) finely divided particles of electrically conductive metal, metal oxide precursors or alloys of the conductive metals, or mixtures thereof, dispersed in (B) an organic medium comprising (1) an organometallic compound, the metal or metal oxide moiety of which is soluble in the electrically conductive metal and/or the oxides of the metal moiety are non-reducing in the presence of electrically conductive metal, the organometallic compound being dissolved in; (2) a solution of polymeric binder in volatilizable solvent.
U.S. Pat. No. 5,244,742, issued to Ogi et al, relates to ultrahigh purity ferroelectric thin films. The thin film of lead containing ferroelectric materials represented by the formula Pb.sub.1-x La.sub.x (Zr.sub.y Ti.sub.1-y).sub.1-x/4 O.sub.3, where Y is 0 or 1 or a decimal smaller than 1, characterized in that the total content of alkali metal impurities therein is less than 1 ppm.
U.S. Pat. No. 5,372,850, issued to Uchikawa et al, relates to a method of manufacturing an oxide-system dielectric thin film using CVD methods. The oxide-system dielectric thin film is coupled with an organic group through oxygen atoms by the CVD method.